Generally, a header flotation capability is desirable to allow the header to ride lightly up and over rises in the terrain during field operation. Full flotation, that is, the capability for both upward and downward movement, may be desired when the header is carried in contact with the ground, to enable cutting plants close to the ground surface while avoiding potentially damaging impacts with raised terrain features and fixed obstacles. An upward flotation or up-float capability, that is, wherein only upward float movements are allowed, may be desired when the header is carried at some elevation or height above the ground, for cutting plants at that height, while riding over obstacles that are encountered at that height. A lift capability is required for moving the header to a desired cutting height, and also to a height above the cutting height, such as for turning in a headland of a field, movement between fields, travel over roads, and the like.
It is known to provide a header height or lift control system which uses an accumulator and hydraulic cylinders to also provide a flotation capability. Such systems typically use separate hydraulic cylinders for the lift and flotation functions, which is disadvantageous cost-wise and in terms of complexity. Many such systems also lack the capability of independently adjusting the flotation force for each side of the header. This can be a shortcoming, as some headers are not inherently balanced side to side. In many cases, special considerations must be made to float and lift these headers evenly by adding ballast, which can become unreasonably heavy or awkward, or modifying the lift geometry of one side.
It has been found to be desirable to have a capability to more easily, and preferably automatically, switch between a ground following or contacting cutting mode wherein a full flotation function is available, and a raised height control mode, having only an up float function. It has also been found that flotation function can degrade over time, as a result of a variety of conditions, particularly changes in header weight and weight distribution, such as can result from build-up or removal of cut plant material, and/or dirt, soil, mud, and the like, on the header. Hydraulic fluid temperature and viscosity variations can also affect flotation function. And, one or more of these conditions can vary during a single plant cutting session, e.g., soil build-up on cutter bar or disk heads, plant material build-up occurs or is removed, making it desirable to have a capability to calibrate or adjust flotation settings frequently for optimal operation, preferably automatically.
Accordingly, what is sought is a method and system for controlling the operation of a header flotation and lift system for a plant cutting machine, which provides dual modes of operation, including a first mode allowing operator settable and controllable header height with an up-float capability, and a second ground contact mode having a full float capability, and which system is automatically operable for switching between the two modes responsive to predetermined input commands, and can automatically calibrate or adjust for changes in header weight and other conditions, and which overcomes one or more of the shortcomings and limitations set forth above.